A semiconductor device includes a metallic plate and a semiconductor element. The semiconductor element is bonded to the metallic plate with a solder so that a heat generated in the semiconductor element is radiated from the metallic plate. The device is disclosed in JP-2005-123233. The device further includes another metallic plate so that the semiconductor element is sandwiched between a pair of the metallic plates. A block is inserted between one of the metallic plates and the semiconductor element. The one of the metallic plates is bonded to the block with a solder. A pair of the metallic plates, the semiconductor element and the block are molded with a resin mold. A heat radiation surface of each metallic plate is exposed from the resin mold so that the metallic pate radiates heat generated in the semiconductor element. Accordingly, the heat in the semiconductor element is radiated from both sides of the element. Thus, the device provides a both-side heat radiation type semiconductor device.
The block between the metallic plate and the element is used for adjusting a clearance between the metallic plates in order to secure a space when multiple semiconductor elements are sandwiched between the metallic plates or when the semiconductor element is connected to a lead terminal with a wire.
In the device, one of the metallic plates, the semiconductor element, the block and the other one of the metallic plates are stacked together. In this case, the semiconductor element and the block are stacked on the one metallic plate in this order, and then the stacked plate, the element and the block are assembled. After that, an assembly turns over so that the block is disposed downward. Then, the assembly is mounted on the other metallic plate. Thus, the assembly with the metallic plate is bonded to the other one metallic plate with a solder.
At this time, a clearance between the metallic plates, i.e., a height of each element in the assembly in a stacking direction may be varied. To increase the tolerance of variation of the height of the element, a large amount of solder is inserted between the block and the metallic plate.
It is necessary to prevent the solder from spreading outside the block. Conventionally, a solder groove for preventing the solder from spreading is formed on a surface of a member, on which the solder is mounted. Specifically, the solder groove is disposed around a part of the member, the part on which an element is mounted with the solder. This is disclosed in, for example, JP-A-2004-335776.
However, in the both-side heat radiation type semiconductor device having the solder groove disposed around the solder, excess solder in the groove may spread through a side of the block, so that the excess solder reaches the semiconductor element. Thus, short-circuit in the element may be occurred.
Further, in another semiconductor device having a semiconductor element bonded to a metallic plate with a solder, excess solder in a solder groove of the device may cause short-circuit. Specifically, the solder is mounted on a part of the metallic plate so that the semiconductor element is bonded to the part of the metallic plate. The solder groove is formed around the part of the metallic plate. In this case, the excess solder in the groove may spread through a side of the semiconductor element, so that the excess solder reaches the surface of the semiconductor element, or the excess solder may overflow from the groove. Thus, the short-circuit is occurred.